The objective is to investigate the usefulness of electro-encephalographic sleep studies and automated sleep-EEG analysis in the differential diagnosis of depression, senile dementia, and depressive pseudo-dementia in persons aged 60 to 69 years. Sleep studies of an age-matched group of normal controls will also be performed. In the depressives, a battery of neuropsychologic tests will be administered before and after treatment with amitriptyline, in order to show whether cognitive function improves with treatment or relief from depression. Correlations between sleep variables and test scores will be explored. The use of the sleep EEG as an aid to enhancing the accuracy and specificity of drug treatment of depression in the elderly will then be explored. In addition, changes in respiration during sleep (i.e., extent of apnea, hypopnea, and oxygen desaturation) will be investigated with relevance to cognitive and psychopathologic variables.